Pellicle and method of manufacturing same

ABSTRACT

A pellicle comprises a stress-controlled metal layer. The stress in said metal layer may be between about 500-50 MPa. A method of manufacturing a pellicle comprising a metal layer includes deposing said metal layer by plasma physical vapor deposition. Process parameters are selected so as to produce a desired stress value in said metal layer, such as between about 500-50 MPa.

PRIORITY

This application claims the benefit to U.S. Provisional PatentApplication No. 62/747,385, filed on Oct. 18, 2018, and entitled“Pellicle and Method of Manufacturing Same” which application isincorporated herein by reference.

TECHNICAL FIELD

This invention relates generally to lithography, and more particularlyto an improved pellicle and a method of manufacturing the same.

BACKGROUND

For decades now, the semiconductor industry has steadily reduced theminimum size of circuit features from one generation of integratedcircuits to the next. Reduced features sizes allow the integration ofgreater levels of functionality on one integrated circuit and reduce thecost for the same functionality. Circuit features are defined bylithography. In lithography, light is patterned according to patternsembedded in reticles, and projected onto layers of a photosensitivematerial disposed on the integrated circuit at various steps during itsmanufacture. In some applications, it is beneficial to keep reticlesclear of particles or contaminants, as their presence can causedistortions in intended patterns. To this end, a pellicle is ofteninstalled in close proximity to the reticle and acts as a shield againstparticles and contaminants. It is widely expected that ExtremeUltraviolet (EUV) lithography, operating at a wavelength of 13.5 nm,will be employed for manufacturing integrated circuits in the nearfuture.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure, and theadvantages thereof, reference is now made to the following descriptionstaken in conjunction with the accompanying drawings, in which:

FIG. 1 is a block diagram of elements of an Extreme Ultra Violet (EUV)lithography system.

FIG. 2 is an illustration of selected components of an EUVreticle-pellicle assembly.

FIG. 3A is an illustration of additive steps in an embodiment of amethod for manufacturing a pellicle comprising a stress-controlledemissivity layer.

FIG. 3B is an illustration of an embodiment of a pellicle comprising astress-controlled emissivity layer.

FIG. 4 is an illustration of selected elements of an exemplarydeposition process.

FIG. 5 is an illustration of stress values measured on first emissivityfilms deposited at different process conditions;

FIG. 6 is an illustration of X-ray diffraction data for first emissivityfilms deposited at a set of illustrative process conditions.

FIG. 7 is an illustration of X-ray diffraction data for first emissivityfilms deposited at a second set of illustrative process conditions.

FIG. 8 is an illustration of stress values measured on first emissivityfilms deposited at selected values of process pressure.

FIG. 9A is an illustration of stress values measured on secondemissivity films deposited at selected values of power.

FIG. 9B is an illustration of the distribution of stress values measuredon second emissivity films deposited at selected values of power.

FIG. 10A is an illustration of stress values measured on firstemissivity films deposited at selected values of power.

FIG. 10B is an illustration of the distribution of stress valuesmeasured on first emissivity films deposited at selected values ofpower.

FIG. 11A is an illustration of stress values measured on two-layerstacks consisting of a second emissivity film and a first emissivityfilms of deposited at selected values of process temperature.

FIG. 11B is an illustration of the distribution of stress valuesmeasured on two-layer stacks consisting of a layer of first emissivityfilm and a second emissivity film deposited at selected values ofprocess temperature.

Corresponding numerals and symbols in different figures generally referto corresponding parts unless otherwise indicated. The figures are drawnto illustrate clearly the relevant aspects of embodiments of the presentdisclosure and are not necessarily drawn to scale. To more clearlyillustrate certain embodiments, a letter indicating variations of thesame structure, material, or process step may follow a figure number.

DETAILED DESCRIPTION

The making and using of embodiments are discussed in detail below. Itshould be appreciated, however, that the present disclosure providesmany applicable inventive concepts that may be embodied in a widevariety of specific contexts. The specific embodiments discussed aremerely illustrative of specific ways to make and use the invention, anddo not limit the scope of the invention. For example, the formation of afirst feature over or on a second feature in the description thatfollows may include embodiments in which the first and second featuresare formed in direct contact, and may also include embodiments in whichadditional features may be formed between the first and second features,such that the first and second features may not be in direct contact. Inaddition, spatially relative terms, such as “below”, “above”, “lower”,“upper”, “beneath”, and the like, may be used herein for ease ofdescription to describe one element or feature's relationship to anotherelement(s) or feature(s) as illustrated in the figures. Spatiallyrelative terms are intended to encompass different orientations of thedevice in use or operation in addition to the orientation depicted inthe figures. The apparatus may be otherwise oriented (rotated 90 degreesor at other orientations) and the spatially relative descriptors usedherein may likewise be interpreted accordingly. Herein, the terms“light” and “radiation” are used interchangeably, as are the terms“reticle” and “mask”.

FIG. 1 is a block diagram of elements of an Extreme Ultra Violet (EUV)lithography system. An EUV lithography system 100 comprises a radiationsource 105, an illuminator 110, a reticle-pellicle assembly 115, aprojection optics module 120, and a target 125. EUV radiation isgenerated in the radiation source 105. Radiation in a range ofwavelengths extending approximately from 10 to 125 nm may be consideredextreme ultraviolet. Plasmas are known to radiate EUV light, and may beproduced in a several ways. A Laser-Produced Plasma (LPP) may begenerated when a laser beam imparts enough energy to a piece of matterto turn it into a plasma. A Discharge-Produced Plasma (DPP) is usuallyproduced when an electric discharge is formed through a gas. EUVlithography systems typically operate at a wavelength of 13.5 nm. Tin(Sn) plasmas are known to radiate light at this wavelength, and they maybe laser-produced. The radiation source 105 may comprise apparatus forgenerating a plasma.

Extreme ultraviolet light generated in the radiation source 105 isdirected to the illuminator 110, which in turn directs the light to thereticle-pellicle assembly 115. The illuminator 110 may comprise a numberof EUV mirrors. All matter absorbs radiation at 13.5 nm. Therefore, EUVlithography systems typically employ reflective optics, rather thanlenses. However, reflection from a single interface between twomaterials is usually too weak to be of use in practical EUV lithography.It is possible to achieve higher reflectively by constructing amulti-layer reflector comprising tens of alternating layers of twomaterials with differing indices of refraction. Multi-layer reflectorsconstructed from layers of molybdenum (Mo) and silicon (Si) commonlyachieve reflectivity values well in excess of 50% at the operatingwavelength of 13.5 nm.

FIG. 2 is an illustration of selected components of an EUVreticle-pellicle assembly. An EUV reticle-pellicle assembly 200comprises a reticle 205 and a pellicle 210. The pellicle 210 may bemounted on the reticle 205 using a mounting frame 215. The reticle 205comprises a substrate 220 and a multi-layer reflector 225. In addition,the reticle 205 comprises one or more regions 230, wherein an EUVabsorber material 235 is disposed on the multi-layer reflector 225, andone or more regions 240, where the absorber material 235 is absent. Theregions 230 and 240 are formed in accordance with a desired pattern ofcircuit features. In the lithography operation, incident EUV light 250arrives at the pellicle 210. A portion of incident EUV light is absorbedin the pellicle 210. The remaining portion passes through the pellicle210 and arrives at the reticle 205. In regions 240, EUV light isreflected from the multi-layer reflector 225. In contrast, in regions230, EUV light is absorbed and not reflected. Light 255 reflected fromthe reticle 205, thus patterned, arrives at the pellicle 210 andsubstantially passes through it.

The reticle 205 depicted in FIG. 2 is commonly referred to as areflective mask. It is realized herein, however, that other types ofreticles may be used in a reticle-pellicle assembly, such as areflective attenuated Phase-Shift Mask (AttPSM) or a reflectivealternating Phase-Shift Mask (AltPSM). In Deep Ultra Violet (DUV)lithography systems, the reticle may be a transmission or phase-shiftreticle on material substantially transparent to the wavelength usedtherein.

Referring to FIG. 1, patterned light reflected from the reticle-pellicleassembly 115 is projected onto the target 125 by the projection opticsmodule 120. The projection optics module 120 commonly comprises EUVmirrors and typically produces an optical magnification less than one,projecting a smaller version of the pattern of the reticle onto thetarget 125. The target 125 may be a substrate having a photosensitivelayer disposed thereon. EUV light thus projected onto the target layerimparts the pattern into the photosensitive layer, and developing thephotosensitive layer realizes the desired pattern over the underlyingtarget. The target substrate may be a semiconductor wafer formed fromsemiconductors such as silicon, germanium, compound semiconductors, andthe like, or a combination thereof. Furthermore, the target substratemay be silicon-on-insulator (SOI), include an epitaxial layers, orcomprise strained areas for performance enhancement. The targetsubstrate may include a plurality of dies formed or partially formedthereon. Each die may include any number of semiconductor devices, suchas field effect transistors (FETs), capacitors, resistors, conductiveinterconnects, or other suitable devices, in various stages offabrication. The target substrate may include various semiconductorregions doped with suitable dopants. Exemplary regions include activeregions on which MOS devices can be formed. The doped regions, includingbut not limited to active regions, may vary in dimension, dopant level,configuration, or other properties. The boundaries of the active regionsmay be defined by isolation structures such as shallow trench isolation(STI) features. Furthermore, one or more layers to be patterned, e.g.,insulative, conductive, and/or semiconductive material, may be formed onthe substrate as well. The photosensitive layer is a material sensitiveto the radiation employed in the lithography system, and may be positivetone or negative tone photoresist. The photosensitive layer may beformed on the target substrate by spin-on coating, soft baking, or othermethods, or combinations thereof. Since EUV light of wavelength 13.5 nmis absorbed in all matter, and in particular in all un-ionized inertgases, the path of EUV light from the radiation source 105 to the target125 is commonly enclosed in vacuum.

FIG. 3A is an illustration of additive steps in an embodiment of amethod for manufacturing a pellicle comprising a stress-controlled metallayer. The method begins with the formation of a first etch-stop layer310 on a silicon wafer 305. In some embodiments, the first etch-stoplayer 310, e.g., AlN, AlO, BN, BO, SiC, SIN, SiO₂, and their relatedcompound, ranges in thickness from about 1000 to about 10000 Å. Thematerial can be stoichiometric, for example, SiO₂ or Al₂O₃, or in otherembodiments non-stoichiometric. In various embodiments, the firstetch-stop layer 310 is deposited, for example by a plasma physical vapordeposition (PVD) and CVD process, or grown thermally. Next, a secondetch stop layer 315 is formed on the first etch-stop layer 310. In someembodiments, the second etch stop layer 315 can be metal or dielectricmaterials such as nickel (Ni), copper (Cu), Molybdenum (Mo), Tungsten(W) or AlN, AlO, BN, BO, SiC, SIN, and SiO. The ranges in thickness fromabout 200 to about 10000 Å, and is deposited by a PVD and CVD process.Next, a non-metal layer 320 is formed on the second etch-stop layer 315.In various embodiments, the non-metal is Si, SiN, SiC, SiO₂, or thelike, and ranges in thickness from about 50 to about 1000 Å. This layercan be single layer or multi-layer for optical properties requirements.Next, a stress-controlled metal layer 325 is formed on the non-metallayer 320. Herein, the term “metal” may include metalloids as well asmetals. Accordingly, in various embodiments, the stress-controlled metallayer 325 is a metal such as Mo, Zr, Nb, B, Ti, Ru, RuNb, RuTi, RuZr,MoSi, ZrSi, NbSi, or NiZrSi, Rh, Pd, and their alloy or the like, and inother embodiments, a metalloid such as Ge. In general terms, the metalis in some embodiments substantially amorphous or semi-crystalline topolycrystalline in structure. In various embodiments, thestress-controlled metal layer 325 ranges in thickness from about 10 toabout 500 Å. In other embodiments, the single stress-controlled metallayer 325, two or more metal layers are used to form a stress-controlledmetal stack, and each layer may be a different metal or alloy. Althoughlight of wavelength 13.5 nm is absorbed in both the non-metal layer 320and the stress-controlled metal layer 325, the thicknesses of theselayers are chosen to be thin enough to limit absorption of the light inthese layers, preferably to no more than a few percent. The stressproperties of the stress-controlled metal layer 325 and processembodiments for its formation are disclosed further below.

FIG. 3B is an illustration of an embodiment of a pellicle comprising astress-controlled metal layer. Starting with the structure illustratedin FIG. 3A, a pellicle 330 is formed as follows. First, the siliconwafer 305 is removed in an optically active area 340, but not in asustaining frame area 345. In various embodiments, the optically activearea 340 and the sustaining frame area 345 may have a variety of shapes,including square, circular, hexagonal, or polygonal, and the shapes ofthe optically active area 340 and the sustaining frame area 345 may bedifferent. In some embodiments, TMAH, EDA, and KOH and like the samesolutions at concentrations ranging from 0.1 to 5M are used to removethe silicon wafer 305 in the optically active area 340. Next, the firstetch-stop layer 310 is removed in an area substantially the same as inthe optically active area 340. In an embodiment, the first etch-stoplayer 310 is AlN, AlO, BN, BO, SiC, SiN, or SiO₂ and is removed. Next,the second etch-stop layer 315 is removed in an area substantially thesame as in the optically active area 340. In an embodiment, the secondetch-stop layer is nickel (Ni), copper (Cu), Molybdenum (Mo), Tungsten(W) and AlN, AlO, BN, BO, SiC, SiN, or SiO₂, and is removed using atypical metal etchant solution such as HF, H₂SO₄, Nitric acid and likethe same being at concentrations ranging from 0.01 to 5 M. In theillustrated embodiment of FIG. 3B, the portions removed of the layers305, 310 and 315 are all of substantially the same shape (i.e., allcorresponding to the size and shape of the optically active area 340).In other embodiments, however, the respective portions removed for thelayers 305, 310, and 315 need not be of the same size or shape,resulting in a different sidewall profile for the optically active area340.

The structure resulting from the above steps is the pellicle 330 thatincludes layers 320 and 325 for protecting a reticle, as describedabove, and also remnants of the layers 305, 310, and 315, which form asustaining frame 350, which may be used sustain the layers 320 and 325.As noted above, the thicknesses of the layers 320 and 325 are chosen tolimit absorption of light therein. As a result, in the optically activearea 340, the pellicle 330 is substantially transparent to EUV light.The pellicle 330 may be further mounted on an additional metallic ordielectric or ceramic, ceramic-glass mounting frame, such as themounting frame 215 illustrated in FIG. 2, and installed on a reticle foroperation in a lithography system. The pellicle 330 may also be mountedsuch that it is removable from the reticle, for replacement or cleaning,to allow for inspection or cleaning of the reticle, or for otherpurposes. It is contemplated herein that the pellicle 330 may be usedadvantageously in lithography systems other than EUV, such as Deep UltraViolet (DUV), X-ray, soft X-ray (SX), or the like.

During the operation of the lithography system, a portion of EUV lightis absorbed in and heats the pellicle. The stress-controlled metal layer325 radiates a portion of the absorbed heat into the surrounding vacuum,raising the rate of heat dissipation of the pellicle, typically to 5 to35 K/ms, and partially cooling the pellicle. In some embodiments,stress-controlled metal layers are employed on both sides of thenon-metal layer 320, enhancing heat dissipation. Control of stress inthe stress-controlled metal layer 325 is advantageous. In particular,low stress enhances the resilience of the metal film and therefore thepellicle against long-term use. The stress here is preferable controlledfrom about 1000 MPa to about 50 MPa, more preferably 500-50 MPa. Alow-stress film offers another advantage as well. Without adequateresilience, the non-metal layer 320 and the stress-controlled layer 325must be mechanically supported within the optically active area 340.Furthermore, any supporting material within the optically active area340 must not significantly absorb or alter the EUV light passing throughthe pellicle. With a low-stress film, such as stress-controlled metallayer 325, such support is unnecessary, and the sustaining frame 350 issufficient to support the reticle.

In various embodiments, the stress-controlled metal layer 325 may beformed using processes such as thermal spraying, plasma spraying, plasmachemical vapor deposition processes, or plasma physical vapor deposition(PVD) processes, including RF-only plasma PVD, DC-only plasma PVD,RF-plus-DC plasma PVD, or pulse-DC plasma PVD. Plasma physical vapordeposition is sometimes referred to as sputtering.

FIG. 4 is an illustration of selected elements of an exemplary plasmaphysical vapor deposition process. A substrate 410 is placed in vacuum.Substrate 410 could be the same substrate 305 illustrated in FIG. 3Aalong with one or more of layer 310, 315 and 320, or other layers, insome embodiments. A target 415 is manufactured from the material to bedeposited on the substrate 410. The material to be deposited may be ametal or a dielectric. For example, if it is desired that a materialsuch as Mo, Zr, Nb, B, Ti, Ru, RuNb, RuTi, RuZr, RuTi, MoSi, ZrSi, NbSior NiZrSi, Rh, Pd, C and their alloy or the like and their compound oralloy be deposited on the substrate 410, the target 415 is made of Mo,Zr, Nb, B, Ti, Ru, RuNb, RuTi, RuZr, RuTi, MoSi, ZrSi, NbSi or NiZrSi,Rh, Pd, and their alloy or the like. Conversely, if it is desired that adielectric such as tantalum oxide be deposited on the substrate 410, thetarget 415 is made of tantalum oxide. The target 415 is commonly largerthan the substrate 410 to improve the uniformity of the deposited film.An inert gas is commonly introduced between the substrate 410 and thetarget 415. Argon (Ar) or Helium (He) is an advantageous inert gas, asit is cost effective, while also resulting in efficient sputtering dueto its relatively high atomic mass. However, it is realized herein thatother gases, inert or not, may be employed in addition to, or in lieuof, Ar in some applications. For example, a mixture of Ar and O₂ may beused to deposit SiO₂ from a Si target, or a mixture of Ar and N₂ may beused to deposit silicon nitride from a Si target.

Herein, DC-only operation is described first. In DC-only operation, a DCvoltage is applied between the substrate 410 and the target 415.Negative DC bias is applied to the target 415 relative to the substrate410. Accordingly, the target 415 is the cathode and the substrate 410 isthe anode. As a result of the application of the DC voltage, an electricfield is established between the substrate 410 and the target 415. Inpractice, the substrate 410 is commonly grounded and the target 415 isat a negative bias with respect to ground. An electron 420 leaves thetarget 415 under the influence of the electric field and is acceleratedtowards the substrate 410. In a chance collision with an inert gas atom425, the electron 420 ionizes the inert gas atom 425, creating a newfree electron 430 and an inert gas ion 435. Since the inert gas ion 435is positively charged, it is accelerated towards the target 415 underthe influence of the electric field. The inert gas ion 435 collides withthe target 415 and ejects a target atom 440 of the target material awayfrom the target 415. The target atom 440, which may be ejected in avariety of directions, may land on the substrate 440, where itcontributes to the formation of a deposited layer 445. It is appreciatedherein that the single ionization event described above is of anexemplary nature and that in practice many ionization events involvingmany electrons and inert gas atoms take place. Furthermore, in additionto electrons leaving the target 415, electrons generated in ionizationevents, such as the electron 430, may also accelerate towards thesubstrate 410 and ionize additional inert gas atoms. Moreover, collisionof the inert gas ion 435 with the target 415 may result in the ejectionof an electron (not shown) from the target 415. Such electrons arereferred to as “secondary electrons”, and may themselves initiateadditional ionization events. In this manner, a plasma comprising manyelectrons and ions is formed between the target 415 and the substrate410, and many atoms are sputtered from the target 415 and form thedeposited film 445.

The efficiency of the deposition process may be enhanced through the useof a magnetron arrangement. In a magnetron PVD deposition system,magnets 450 may be used to generate a magnetic field in the vicinity ofthe target. A magnetic field line 455 illustrates the direction of theresulting magnetic field, indicating that the directions of the magneticand electric fields are approximately perpendicular to each other overmuch of the target. Such “crossed” magnetic and electric fields confineelectrons, and therefore substantially the plasma, to the vicinity ofthe target 415. This confinement reduces the probability of deleteriouscollisions between electrons and the substrate 410, and increases theefficiency of the deposition process.

During the deposition process, each inert gas ion 435 arriving at thetarget 415 imparts a positive charge to the target 415. If the target415 is conducting, as in the case of targets made of metal, this chargeis drained away through the bias circuitry. If, however, the targetmaterial is a dielectric, a significant positive charge can collect atthe target over time, eventually leading to the quenching of the plasmaaltogether. A solution to this problem is to use an RF bias instead of aDC bias. With an RF bias, the positive charge collected on the targetduring each half cycle is canceled during the succeeding half cycle,preventing a significant charge buildup over time. An RF voltage at afrequency of 13.56 MHz is commonly used in physical vapor depositionsystems, since this frequency is reserved for industrial applications.In DC-plus-RF PVD, both DC and RF biases are available for use incombination.

In addition to DC power, RF power, and duty cycle, process temperature,process pressure, and process spacing are among the parameters affectingthe deposition process. The process temperature is the temperature ofthe substrate during deposition. If a single gas is used, the processpressure is the pressure of said gas in the process chamber. If multiplegases are employed, the partial pressure of each gas may affect theprocess. The process spacing is the spacing between the target and thesubstrate.

Referring to FIG. 3B, in one embodiment, the stress-controlled metallayer 325 is deposited on the dielectric layer 320 using a DC-only, RF,or RF-plus-DC plasma PVD process. Process pressure, temperature, DCpower, RF power, duty cycle, and spacing are chosen to control thestress embedded in the stress-controlled metal layer 325.

In an embodiment, process temperature and DC power are selected to fromabout room temperature and 150 W, respectively, to control stress in apellicle metal film. FIG. 5 is an illustration of stress values measuredon ruthenium films deposited at room temperature and a power of 150 W,as well as ruthenium films deposited at a temperature of 100° C. and DCpower of 450 W. Positive stress values indicate tensile stress. Ru filmsdeposited at relatively higher temperature of 100° C. and DC power of450 W exhibit relatively high stress values in excess of 300 MPa. Incontrast, Ru films deposited at room temperature and a relatively lowerDC power of 150 W exhibit low stress values below 300 MPa.

In addition, stress values associated with the lower temperature and DCpower settings exhibit lower variation between different films,indicating that lower stress is achieved with better control andconsistency. Lower variation is advantageous because it raises themanufacturing yield of pellicles. When variation is high, even if themean stress value itself is low, some percentage of pellicles producedexhibit high stress and must be discarded. This lowers the pelliclemanufacturing yield and increases the total production cost of usablereticles.

FIG. 6 is an illustration of X-ray diffraction data for ruthenium filmsdeposited at 100° C. and a DC power of 450 W. As noted above, such filmsgenerally exhibit higher stress than films deposited at room temperatureand a DC power of 150 W. A region 605 of the data encompassesdiffraction from (100), (002), and (101) crystalline planes. FIG. 7 isan illustration of X-ray diffraction data for ruthenium films depositedat room temperature and a DC power of 150 W. As noted above, such filmsgenerally exhibit lower stress than films deposited at a temperature of100° C. and a DC power of 450 W. A region 705 of the data encompassesdiffraction from (100), (002), and (101) crystalline planes. In theregion 605 of FIG. 6 and the region 705 of FIG. 7, strong and distinctpeaks in the data may be expected for highly crystalline films, and abroad and diffuse bulge may be expected for less crystalline and moreamorphous films. Visual comparison of the data in the regions 605 and705 suggests that relatively stronger peaks are present in the region605 compared to the region 705. This indicates that relative to thehigher-stress emissivity film deposited at condition 2, the lower-stressRu film deposited at condition 1 has a more amorphous to semi-crystaltexture. Quantitative analyses of the data can also be used to estimatethe strengths of any peaks corresponding to diffraction from (100),(002), and (101) planes embedded in and contributing to the diffractionsignal in the regions 605 and 705. Table 1 contains such estimates forthe two films. Estimated peak strengths are relatively lower for thelower-stress Ru film deposited at room temperature and a DC power of 150W, indicating that the texture of this film is relatively moreamorphous. In contrast, estimated peak strengths for the Ru filmdeposited at 100° C. and a DC power of 450 W are relatively higher,indicating that this film has higher crystalline content. Estimated peakstrengths obtained from quantitative analysis of the data thus confirmthe earlier conclusion from visual inspection.

TABLE 1 Crystalline planes (100) (002) (101) 100° C., 450 W DC 5 4 12Room Temperature, 150 W DC 2.8-3.2 1.9-2.1 4.5-5.5

In another embodiment, a process pressure of 15 mT or 20 mT is selectedto control stress in a pellicle metal film. FIG. 8 is an illustration ofstress values measured on emissivity films deposited at selected valuesof process pressure. Emissivity films deposited at a process pressure of10 mT and three DC power settings ranging from 100 W to 450 W exhibithigh tensile stress, with measured stress values over 300 MPa. Bycontrast, Ru films deposited at process pressures of 15 mT and 20 mT,and the same three DC power settings ranging from 100 W to 450 W,exhibit low tensile stress values below 300 MPa. As described above, thespread in measured stress values is also of interest. Wide spread lowersthe pellicle manufacturing yield. The spread in measured stress valuesfor Ru films deposited at a process pressure of 10 mT across the threeDC power selections is approximately 400 MPa, with stress values as highas 700 MPa measured. For Ru films deposited at process pressures of 15mT and 20 mT, however, the spread in measured stress values across allthree DC power settings is lower than 100 MPa and just over 100 MPa,respectively, allowing all measured values to remain below 300 MPa.

It should be appreciated that multiple process parameters may be setwithin ranges to control the stress of a pellicle emissivity film. In anembodiment, a process pressure between 5 mT and 25 mT, a processtemperature between 15° C. and 300° C., a DC power between 50 W and 400W, and an RF power between 50 W and 1800 W, a duty cycle between 30% and80%, and a process spacing of 50 mm and 250 mm are selected to controlthe stress in a pellicle metal film. These ranges are summarized inTable 2.

TABLE 2 Parameter Range Pressure (mT) 5-25 Temperature (° C.) 15-300 DCpower (W) 50-400 RF power (W)  50-1800 Duty Cycle (%) 30-80  Spacing(mm) 50-250

The manner of usage of embodiments of a pellicle comprising astress-controlled emissivity layer is similar to that of otherpellicles. As shown in FIG. 2, the pellicle is installed on a reticle toprotect the reticle from particles and contaminants. It may also beremovable from the reticle, for replacement, to allow inspection of thereticle, or for other purposes. The manner of usage of a process tocontrol the stress in a pellicle emissivity film is to use processsettings of disclosed embodiments or similarly advantageous settingswithin the ranges disclosed in Table 2 in an RF-plus-DC plasma PVD orCVD system. While differences in different deposition systems may resultin differences in the precise settings to achieve precisely the sameprocess conditions, such differences are widely appreciated and arecommonly taken into account without undue experimentation.

One general aspect of embodiments disclosed herein includes a pellicleincluding: an optically active area; a non-metal layer extending overthe optically active area; and a stress-controlled metal layer on thenon-metal layer and extending over the optically active area, where astress in said metal layer is between about 5000-50 MPa

Another general aspect of embodiments disclosed herein includes methodof manufacturing a pellicle comprising depositing a non-metal layer overa substrate; and depositing a emissivity layer over the non-metal layer,wherein a stress in said emissivity layer is between about 500-50 MPa.The stress can be tensile or compressive.

Yet another general aspect of embodiments disclosed herein includes adevice including: a reticle having an optically active area, the reticleconfigured for use in an exposure system employing radiation of apreselected wavelength; and a pellicle mounted to the reticle, thepellicle including, a second optically active area corresponding to theoptically active area of the reticle, a non-metal layer extending overthe second optically active area, the non-metal layer beingsubstantially transparent to the radiation of a preselected wavelength,and a stress-controlled metal layer on the non-metal layer and extendingover the optically active area, the stress-controlled emissivity layerhaving a stress between 500-50 MPa. The stress can be tensile orcompressive.

It will also be readily understood by those skilled in the art thatmaterials and methods may be varied while remaining within the scope ofthe present disclosure. It is also appreciated that the presentdisclosure provides many applicable inventive concepts other than thespecific contexts used to illustrate embodiments. Accordingly, theappended claims are intended to include within their scope suchprocesses, machines, manufacture, compositions of matter, means,methods, or steps.

What is claimed is:
 1. A pellicle comprising: an optically active area;a non-metal layer extending over the optically active area; and astress-controlled metal layer on the non-metal layer and extending overthe optically active area, wherein a stress in the stress-controlledmetal layer is between about 50-500 MPa.
 2. The pellicle of claim 1,wherein said stress-controlled metal layer is substantially amorphous,semi-crystal to polycrystalline structure.
 3. The pellicle of claim 1,wherein the stress-controlled metal layer is selected from the groupconsisting of ruthenium, molybdenum, rhodium, palladium, niobium, andgermanium.
 4. The pellicle of claim 1, further comprising a sustainingframe comprising a silicon layer.
 5. The pellicle of claim 4, whereinthe sustaining frame comprises at least one etch stop layer over thesilicon layer.
 6. The pellicle of claim 4, wherein the non-metal layerextends between the sustaining frame and the stress-controlled metallayer.
 7. The pellicle of claim 1, further comprising a secondstress-controlled metal layer and wherein the non-metal layer isinterjacent the stress-controlled metal layer and the secondstress-controlled metal layer.
 8. A method of manufacturing a pelliclecomprising: depositing a non-metal layer over a substrate; anddepositing a metal layer over the non-metal layer, wherein a stress insaid metal layer is between about 50-500 MPa.
 9. The method of claim 8,further comprising depositing said metal layer in a substantiallyamorphous, semi-crystal to poly crystal state.
 10. The method of claim8, further comprising patterning the substrate to form a sustainingframe.
 11. The method of claim 10, further comprising depositing an etchstop layer over the substrate prior to depositing the non-metal layerand patterning the etch stop layer to form said sustaining frame. 12.The method of claim 8, further comprising depositing a secondstress-controlled metal layer over the substrate before depositing thenon-metal layer.
 13. The method of claim 8, wherein the metal layer isdepositing by plasma physical vapor deposition.
 14. The method of claim13, wherein the plasma physical vapor deposition is performed at one ormore of the following conditions: a process pressure in the range of 5to 25 mT, a process temperature in the range of 15 to 300 degreesCelsius, a DC power in the range of 50 to 400 W, an RF power in therange of 50 to 1800 W, a duty cycle in the range of 30 to 80%, and aprocess spacing in the range of 50 to 250 mm.
 15. A method ofmanufacturing a device comprising: directing illumination at areticle-pellicle assembly, the reticle-pellicle assembly including: areticle having an optically active area, the reticle configured for usein an exposure system employing radiation of a preselected wavelength;and a pellicle mounted to the reticle, the pellicle including, a secondoptically active area corresponding to the optically active area of thereticle, a non-metal layer extending over the second optically activearea, the non-metal layer being substantially transparent to theradiation of the preselected wavelength, and a stress-controlledemissivity layer on the non-metal layer and extending over the opticallyactive area, the stress-controlled emissivity layer having a stressbetween 50-500 MPa; using a pattern on the reticle-pellicle assembly,selectively reflecting portions of the illumination onto a substrate topattern a layer on the substrate.
 16. The method of claim 15, whereinselectively reflecting portions of the illumination onto a substratecomprises absorbing portions of the illumination with an absorbermaterial in portions of the optically active area and reflecting secondportions of the illumination from second portions of the opticallyactive area.
 17. The method of claim 15, further comprising the stepsof: manufacturing the reticle-pellicle assembly by: depositing anon-metal layer over a substrate; and depositing a metal layer over thenon-metal layer, wherein a stress in said metal layer is between about50-500 MPa; patterning the substrate to form a sustaining frame;depositing an etch stop layer over the substrate prior to depositing thenon-metal layer and patterning the etch stop layer to form saidsustaining frame; and depositing a second stress-controlled metal layerover the substrate before depositing the non-metal layer.
 18. The methodof claim 17, wherein the metal layer is depositing by plasma physicalvapor deposition using one more of the following conditions: a processpressure in the range of 5 to 25 mT, a process temperature in the rangeof 15 to 300 degrees Celsius, a DC power in the range of 50 to 400 W, anRF power in the range of 50 to 1800 W, a duty cycle in the range of 30to 80%, or a process spacing in the range of 50 to 250 mm.
 19. Themethod of claim 15, wherein the step of using a pattern on thereticle-pellicle assembly, selectively reflecting portions of theillumination onto a substrate to pattern a layer on the substrateincludes exposing a photoresist layer on the substrate to Extreme UltraViolet (EUV) radiation.
 20. The method of claim 17, wherein the step ofdepositing a metal layer over the non-metal layer comprises depositing ametal selected from the group consisting of ruthenium, molybdenum,rhodium, palladium, niobium and germanium; and wherein the metal layerextends over one surface of the non-metal layer, and further comprisingthe second stress-controlled metal layer extending over an oppositesurface of the non-metal layer.